About filtration

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dw1305
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Re: About filtration

Post by dw1305 »

Hi all,
Boris wrote: Mon Aug 03, 2020 1:48 pmYes, I understand that but if the plant didn't release oxygen from the roots, the same ammonia that reached this zone would not be nitrified and could be taken up by the plant at less cost. The plant is "giving" the bacteria the oxygen that it then has to reduce again.
It is really all down to amounts, any available ammonia is going to be taken up by nitrifying micro-organisms and plants and it is never going to accumulate and will always be below 1 ppm. It is different for nitrate, it isn't as energy rich, so can build up to ~30 ppm even in natural situations.

cheers Darrel
dw1305
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Re: About filtration

Post by dw1305 »

Hi all,
Boris wrote: Mon Aug 03, 2020 2:03 pmI have Walstads book on its way in the mail but I have not read it. However I have suspicions that she is attributing too much to the plants and too little to microbes.
No I don't think she is. It is always plant/microbe nitrification when you have plants, and since she wrote her book there has been a lot of scientific work that has shown that plant/microbe biofiltration can potentially deal with much larger bioloads (an order of magnitude larger) than "microbe only" filtration. (From th linked paper "Myriophyllum aquaticum Constructed Wetland Effectively Removes Nitrogen in Swine Wastewater")
In this study, a three-stage surface flow CW was constructed in a pilot-scale within monospecies stands of Myriophyllum aquaticum to treat swine wastewater. Steady-state conditions were achieved throughout the 600-day operating period, and a high (98.3%) average ammonia removal efficiency under a N loading rate of 9 kg ha-1 d-1 was observed. To determine whether this high efficiency was associated with the performance of active microbes, the abundance, structure, and interactions of microbial community were compared in the unvegetated and vegetated samples. Real-time quantitative polymerase chain reactions showed the abundances of nitrifying genes (archaeal and bacterial amoA) and denitrifying genes (nirS, nirK, and nosZ) were increased significantly by M. aquaticum in the sediments, and the strongest effects were observed for the archaeal amoA (218-fold) and nirS genes (4620-fold). High-throughput sequencing of microbial 16S rRNA gene amplicons showed that M. aquaticum greatly changed the microbial community, and ammonium oxidizers (Nitrosospira and Nitrososphaera), nitrite-oxidizing bacteria (Nitrospira), and abundant denitrifiers including Rhodoplanes, Bradyrhizobium, and Hyphomicrobium, were enriched significantly in the sediments.
To get around the uncertainty of what goes where researchers have used the differing isotopes of nitrogen to try and find out where fixed nitrogen ends up.

I'm not sure which papers everyone has access to, but "<Plant diversity increases N removal in constructed wetlands when multiple rather than single N processes are considered">says
(3) isotope fractionation in the rhizosphere of Coix lacryma‐jobi was primarily due to microbial denitrification while multistep isotope fractionation was detected for Phragmites australis and Acorus calamus (indicating recycling of N), suggesting that species differed in the way they transformed N; (4) the enhanced N removal at high diversity may be due to mutualistic interactions among species belonging to different functional types. Our findings demonstrated that although plant species richness had negligible effects on individual N‐cycling processes, it enhanced the overall ecosystem functioning (N removal) when these processes were considered collectively.
cheers Darrel
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Re: About filtration

Post by Lycosid »

Boris wrote: Mon Aug 03, 2020 2:03 pm I have Walstads book on its way in the mail but I have not read it.
However I have suspicions that she is attributing too much to the plants and too little to microbes.
I have Walstad's book. I thought it was very good.

Disclaimer: I also know Diane Walstad (although not well).
Disclaimer to the disclaimer: this means I also know that she raises a lot of fish (especially fancy guppies, these days) and takes her own advice, sometimes running experiments to verify ideas. So while she could be mistaken about why something works she's promoting ideas that she has made work, and my impression is that she is generally careful and cautious.
dw1305
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Re: About filtration

Post by dw1305 »

Hi all,
Lycosid wrote: Mon Aug 03, 2020 8:33 pmI have Walstad's book. I thought it was very good......... I also know that she raises a lot of fish (especially fancy guppies, these days) and takes her own advice, sometimes running experiments to verify ideas. So while she could be mistaken about why something works she's promoting ideas that she has made work, and my impression is that she is generally careful and cautious.
I think the passage of time has made it even more impressive as a book.

No-one else has attempted to write anything of similar scope, and, while you might not agree with absolutely everything in it, 99% of it is veritable gold-dust.

It is the book I wish I'd written.

I really admire both Diana Walstad and Tim Hovanec for having embraced scientific change and revised their opinion based on more recent research (either their own, or by other scientists).

I started posting about "cycling" based on our findings from working on the phytoremediation of waste-water. It was before I knew about all the novel nitrifyng micro-organisms, but I was pretty sure the linear view of cycling wasn't right.

cheers Darrel
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Re: About filtration

Post by dw1305 »

Hi all,
TwoTankAmin wrote: Mon Aug 03, 2020 5:15 pm..........I have posted this before.

Petersen, Nils Risgaard‐, Jensen, Kim, (1997), Nitrification and denitrification in the rhizosphere of the aquatic macrophyte Lobelia dortmanna L., Limnology and Oceanography, 42, doi: 10.4319/lo.1997.42.3.052
https://aslopubs.onlinelibrary.wiley.co ... .42.3.0529

It is an older paper but it is still a good indication of what can occur in a planted substrate.
There is an updated paper on the effects of Lobelia dortmanna on rhizosphere microbial assemblages:
"The effect of Lobelia dortmanna L. on the structure and bacterial activity of the rhizosphere". K Lewicka-Rataj, A Świątecki, D Górniak - Aquatic botany, 2018

I have access if any-one wants a copy? But the key findings were:
  • The significant influence of L. dortmanna on microbiological processes in the sediments was confirmed. Clearly the high amount, biomass and metabolic and physiological activity of bacteria in the rhizosphere sediments confirmed the stimulating effect of isoetids on sediment bacteria.
  • High redox potential and high bacterial respiration rate in the rhizosphere.
  • High DOC concentration results in high bacterial activity in rhizosphere.
  • CO2 concentration in rhizosphere depends on the number of active bacteria cells.
cheers Darrel
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Re: About filtration

Post by Boris »

Thank you all three for the links and info!

I am not claiming to contradict Walstad or anyone else. I am simply going through the process where I learn something, think about it, have an idea and then learn why my idea was not correct.

While waiting for Walstad's book to arrive I have done another experiment:

In a 12 gallon I covered the bottom with 1/2" of soil from my dads garden compost. On top of that at least 2" of sand. I used a 50/50 mix of sand/gravel and made a gradient so there is 1 1/2" at front and 3" at the back.
Small sponge filter, two air stones.
No plants! Add water and measure nitrogen.
Expectation:
Image

I don't know how to display a table here.
Result:
Day: 1 3 5 7 8
NH: 0.2, 0.4, 0, -, 0, 0
NO2: 0.5, 0.4, 0.5, 0.1, -, 0
NO3: 5, 5, 10, -, 0,...1,...

Day nine I added 10 small tetras. Day 17 I added another 20 tetras.
Six weeks in nitrate is constant at 1ppm.

So in 8 days I had not only ammonia and nitrite but also nitrate go to zero.
I assume that the necessary amounts of bacteria were present in the soil as a sort of "instant cycle"?

One caveat is I later learned that the "soil" is actually 100% leaf detritus.
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Re: About filtration

Post by aquaholic »

I am not going to get into the filtration discussion but if you wish to have a low maintenance tank, apart from low stocking rate, I would utilise automatic water change. If you add an overflow, you can apply slow continous drip 24/7 to diplace tank water out. Adding new water in drips allows you to use low pressure piping (very cheap) and your drainage line could be as small as airline tube. If you are adding 3% or less of tank volume daily, you do not need to worry about removing chlorine or chloramine. You do not need to be cleaning filters. You do not need to worry about temperature fluctuations in winter. The auto water change will reduce your maintenance routine, save time and increase safety margin for livestock whether you have one tank or several hundred tanks.
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Re: About filtration

Post by Boris »

aquaholic wrote: Wed Aug 05, 2020 8:31 am if you wish to have a low maintenance tank, apart from low stocking rate, I would utilise automatic water change.
Yes, automatic water change is a future plan and apart from reducing maintenance it adds stability which may be an underrated quality in our fish keeping?
The only(?) drawback of this is that it is still a wasteful way. The past years have had reoccurring limits to water sources and consequently water usage around the world and even where I live. Reducing the volume of water needed may become increasingly important.

However a certain amount of water change may be necessary for other reasons than nitrogen.
What other reasons are there for small, but reoccurring water changes?
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Re: About filtration

Post by Bas Pels »

Apart from nitrogen, it looks like fish, at least some species, produce pheromones, reducing the ability of conspecifics to grow.

From my own experience, a single fish in a tank will grow, whether I change water or not. If there are more in the tank, growth will reduce if I don't change water, even if the amount of fish is the same (thus the amount of non-conspecifics is less in case of more conspecifics)

I did not read about it, anywhere, but there does seem to be something
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Re: About filtration

Post by TwoTankAmin »

Your tap water contains a number of things. Some might evaporate, some may get taken into the fish, some get used by plants. Your fish produce waste that is not merely ammonia. Over time things that are needed get used up. Carbonates are a good example. Things that are not used up because they are not needed can build up and that may cause harm. Other things will get depleted. So think of water changes as restoring the balance to the water.

Every system is different. In my case weekly large water changes work well because we have our own well, so that is what I do. For others a drip/overflow systems works best. There are many ways to deal with water changes and multiple ways to drain and refill. But the goals is always the same, remove the unwanted and replace the used up.
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Re: About filtration

Post by aquaholic »

My comment was aimed at reducing tank mainenance as that was the origional quest. If someone strives to water change 20% of a tank once a month, simply set the auto water change amount to replace the same 20% once a month. No net loss in water wastage but a big savings in time, reliability and effort.

There are other ways to conserve water, re-use, rainfall capture, ground water, solar evaporators, etc. As previously mentioned, you can reuse water on non conspecific species to reduce growth hormone limitations but unfortunately fish keeping generally is very wasteful on water. If water is a scarce resource then giving up on keeping fish would be the most environmentally responsible thing to do.

If water conservation is less of a priority, you can use water change to totally replace filtration or allow the filtration to be more of a backup. Many of the houses along rivers in SE Asia use cages to grow fish for food. The fish eat food scraps and the river sweeps and cleans constantly so there is no constraint on growth. I've seen huge 80cm sized fish grown up with tiny 100cm cages.

Also not especially relevant but if your town water supply has occasional and unpredictable bad water issues, the 24/7 auto water change is definitely for you. I've lost half a fish room (80 tanks) doing a manual water change on a bad water day. Implementing auto water change has enabled me to add 2 more fish rooms. I'm still time poor but this is my suggestion for lowering maintenance.
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